Pressure roller containing a volume of fluid

ABSTRACT

A pressure roller for a media processing device has enhanced temperature uniformity and resists temperature increases when subjected to elevated temperatures, enabling greater dimensional stability of the pressure roller in fluctuating temperatures. The pressure roller includes a hollow cylindrical member, an elastomeric layer, and an endbell on each end of the hollow cylindrical member. A chamber is defined by an inner wall of the hollow cylindrical member and the endbells in which a volume of fluid is contained to absorb heat from the hollow cylindrical member.

TECHNICAL FIELD

This disclosure relates generally to pressure rollers for imagingdevices, and, in particular, to pressure rollers configured to reducewrinkling in media.

BACKGROUND

In general, inkjet printing machines or printers include at least oneprinthead that ejects drops or jets of liquid ink onto a recording orimage forming surface. A phase-change inkjet printer employs phasechange inks that are solid at ambient temperature, but transition to aliquid phase at an elevated temperature. The melted ink can then beejected onto print media or an image receiving member by a printhead inresponse to firing signals received from a controller.

In a direct-to-media printer, the printheads eject ink drops directlyonto print media, for example, paper sheets or a continuous media web.After ink drops are printed on the print media, the printer moves theprint media through a nip formed between two rollers that apply pressureand, optionally, heat to the ink drops and print medium. One roller,typically referred to as a “spreader roller,” contacts the printed sideof the print media. The second roller, typically referred to as a“pressure roller,” presses the media against the spreader roller tospread the ink drops and fix the ink to the print media.

Pressure rollers typically include a steel cylindrical core coated by anelastomeric layer. During long substantially continuous printing, thetemperature of the pressure roller can become elevated due to contactwith the heated spreader roller and the print media, which is alsoheated prior to spreading. Temperature differences along the axiallength of the steel core can cause the pressure roller to expand in somelocations along the axis of the core, particularly near the center.Non-uniform expansion of the roller alters the shape of the contact thepressure roller makes with the spreader roller, also known as the “nipprofile.” Changes in the nip profile can result in the print mediawrinkling while traveling through the nip, particularly in continuousmedia printers. Wrinkling of the print media through the spreader canresult in image defects in the printed product.

Temperature increases in the pressure roller caused by its use to helpspread ink on the media also alters the properties of the elastomericlayer on the roller. For example, in some pressure rollers, increasedheating can cause a reduction in the modulus of elasticity of theelastomeric layer. A decreased modulus of elasticity can further impactthe nip profile, compounding the media wrinkle issues noted above.Therefore, improvements in the temperature resistance and uniformity ofpressure rollers are desirable.

SUMMARY

In one embodiment, a pressure roller for a media processing device hasenhanced temperature uniformity and resists temperature increases whensubjected to elevated temperatures, enabling greater dimensionalstability of the pressure roller in fluctuating temperatures. Thepressure roller comprises a hollow cylindrical member, an elastomericlayer, a first endbell, a second endbell, and a volume of fluid. Thehollow cylindrical member includes a first end, a second end, an innercylindrical wall, and an outer cylindrical wall. The inner cylindricalwall forms a chamber that extends between diametrically opposed portionsof the inner cylindrical wall around an entire circumference of theinner cylindrical wall and that extends from the first end to the secondend of the hollow cylindrical member. The elastomeric layer ispositioned immediately adjacent to the outer cylindrical wall andsurrounds the outer cylindrical wall from the first end to the secondend of the hollow cylindrical member. The elastomeric layer defines anouter surface of the pressure roller. The first endbell is sealinglyconnected to the first end of the hollow cylindrical member, and thesecond endbell is sealingly connected to the second end of the hollowcylindrical member. The volume of a fluid is located within the chamber,and fills no more than ninety-five percent of the chamber. The fluidabsorbs heat transferred to the hollow cylindrical member by anotherroller forming a nip with the hollow cylindrical member and distributesthe heat absorbed by the hollow cylindrical member throughout the fluidas the hollow cylindrical member rotates to enable uniform thermalexpansion of the hollow cylindrical member in the nip.

In another embodiment, a pressure roller for a media processing devicehas enhanced temperature uniformity and resists temperature increaseswhen subjected to elevated temperatures, enabling greater dimensionalstability of the pressure roller in fluctuating temperatures. Thepressure roller comprises a hollow cylindrical member, an elastomericlayer, a first endbell, a second endbell, a solid rod, and a volume offluid. The hollow cylindrical member includes a first end, a second end,an inner cylindrical wall, and an outer cylindrical wall. The innercylindrical wall forms a chamber that extends between diametricallyopposed portions of the inner cylindrical wall around an entirecircumference of the inner cylindrical wall and that extends from thefirst end to the second end of the hollow cylindrical member. Theelastomeric layer is positioned immediately adjacent to the outercylindrical wall and surrounds the outer cylindrical wall from the firstend to the second end of the hollow cylindrical member. The elastomericlayer defines an outer surface of the pressure roller. The first endbellis sealingly connected to the first end of the hollow cylindricalmember, and the second endbell is sealingly connected to the second endof the hollow cylindrical member. The solid rod extends axially throughthe center of the hollow cylindrical member from the first endbell tothe second endbell. The volume of a fluid is located within the chamber,and fills no more than ninety-five percent of the chamber. The fluidabsorbs heat transferred to the hollow cylindrical member by anotherroller forming a nip with the hollow cylindrical member and distributesthe heat absorbed by the hollow cylindrical member throughout the fluidas the hollow cylindrical member rotates to enable uniform thermalexpansion of the hollow cylindrical member in the nip.

In yet another embodiment, a printing machine includes a pressure rollerthat has enhanced temperature uniformity and resists temperatureincreases when subjected to elevated temperatures, enabling greaterdimensional stability of the pressure roller in fluctuatingtemperatures. The printing machine comprises a first roller, a secondroller, a plurality of printheads, and a media transport. The secondroller includes a hollow cylindrical member, an elastomeric layer, afirst endbell, a second endbell, and a volume of fluid. The hollowcylindrical member has a first end, a second end, an inner cylindricalwall, and an outer cylindrical wall. The inner cylindrical wall forms achamber that extends between diametrically opposed portions of the innercylindrical wall around an entire circumference of the inner cylindricalwall and that extends from the first end to the second end of the hollowcylindrical member. The elastomeric layer of the second roller ispositioned immediately adjacent to the outer cylindrical wall of thehollow cylindrical member and surrounds the outer cylindrical wall fromthe first end to the second end of the hollow cylindrical member. Thefirst endbell is sealingly connected to the first end of the hollowcylindrical member, and the second endbell is sealingly connected to thesecond end of the hollow cylindrical member. The volume of a fluid islocated within the chamber, and fills no more than ninety-five percentof the chamber. The fluid absorbs heat transferred to the hollowcylindrical member by the first roller, which forms a nip with thehollow cylindrical member of the second roller, and distributes the heatabsorbed by the hollow cylindrical member throughout the fluid as thehollow cylindrical member rotates to enable uniform thermal expansion ofthe hollow cylindrical member in the nip. The plurality of printheadsare configured to eject ink drops onto a media web, which issubsequently moved through the nip by the media transport to spread theink drops and form an ink image on the media web.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of a continuous feed direct to mediaprinter including a fluid-containing pressure roller.

FIG. 2 is a cross-sectional view of the fluid-containing pressure rollerof the printer of FIG. 1.

FIG. 3 is a cross-sectional view of a fluid-containing pressure rollerhaving internal fins.

FIG. 4 is a cross-sectional view of a fluid-containing pressure rollerhaving internal paddles.

FIG. 5 is a cross-sectional view of a fluid-containing pressure rollerhaving a solid core with fins.

FIG. 6 is a cross-sectional view of a fluid-containing pressure rollerhaving a solid core with paddles.

DETAILED DESCRIPTION

For a general understanding of the present embodiments, reference ismade to the drawings. In the drawings, like reference numerals have beenused throughout to designate like elements. As used herein, the terms“printer,” “printing device,” or “imaging device” generally refer to adevice that produces an image with one or more colorants on print mediaand may encompass any such apparatus, such as a digital copier,bookmaking machine, facsimile machine, multi-function machine, or thelike, which generates printed images for any purpose. Image datagenerally include information in electronic form which are rendered andused to operate the inkjet ejectors to form an ink image on the printmedia. These data can include text, graphics, pictures, and the like.The operation of producing images with colorants on print media, forexample, graphics, text, photographs, and the like, is generallyreferred to herein as printing or marking. Phase-change ink printers usephase-change ink, also referred to as a solid ink, which is in a solidstate at room temperature but melts into a liquid state at a higheroperating temperature. The liquid ink drops are printed onto an imagereceiving surface in either a direct or indirect printer.

As used herein, the term “media processing device” refers to a devicethat is configured to perform processing operations on a substrate, suchas paper, either in web or cut-sheet form. The media processing devicecan be, for example, a printing device, a laminating machine, or anyother device through which media substrate is transported using rollersand/or belts.

The term “printhead” as used herein refers to a component in the printerthat is configured with inkjet ejectors to eject ink drops onto an imagereceiving surface. A typical printhead includes a plurality of inkjetejectors that eject ink drops of one or more ink colors onto the imagereceiving surface in response to firing signals that operate actuatorsin the inkjet ejectors. The inkjets are arranged in an array of one ormore rows and columns. In some embodiments, the inkjets are arranged instaggered diagonal rows across a face of the printhead. Various printerembodiments include one or more printheads that form ink images on animage receiving surface. Some printer embodiments include a plurality ofprintheads arranged in a print zone. An image receiving surface, such asa print medium or the surface of an intermediate member that carries anink image, moves past the printheads in a process direction through theprint zone. The inkjets in the printheads eject ink drops in rows in across-process direction, which is perpendicular to the process directionacross the image receiving surface.

In a direct-to-media printer, the printheads eject ink drops directlyonto a print media, for example, a paper sheet or a continuous mediaweb. After ink drops are printed on the print media, the printer movesthe print media through a nip formed between two rollers that applypressure and, optionally, heat to the ink drops and print media. Oneroller, typically referred to as a “spreader roller” contacts theprinted side of the print medium. The second roller, typically referredto as a “pressure roller,” presses the media against the spreader rollerto spread the ink drops and fix the ink to the print media. In indirectprinters, the printheads eject ink drops onto an intermediate membersurface, such as the surface of a rotating drum or belt, and theresulting ink image is passed through a nip formed between the rotatingsurface and a pressure roller, which is sometimes referred to as a“transfix” or “transfer” roller, in synchronization with print media.The pressure and sometimes heat in the nip transfer the ink image fromthe intermediate member surface to the media, which is subsequentlytreated at additional heating and spreading stations to further fix theink image to the print media.

FIG. 1 depicts a schematic view of an inkjet printer 5 having afluid-containing pressure roller 100. For the purposes of thisdisclosure, an inkjet printer employs one or more inkjet printheads toeject drops of ink into an image receiving member, such as paper,another type of print media, or an indirect member such as a rotatingimage drum or belt. The printer 5 is configured to print ink images witha “phase-change ink,” by which is meant an ink that is substantiallysolid at room temperature and that transitions to a liquid state whenheated to a phase change ink melting temperature for jetting onto theimaging receiving member surface. In other embodiments, the ink utilizedin the printer comprises UV curable gel inks, which are also heatedbefore being ejected by the inkjet ejectors of the printhead. As usedherein, liquid ink refers to melted phase change ink, heated gel ink, orother forms of ink, such as aqueous inks, ink emulsions, inksuspensions, ink solutions, or the like.

The printer 5 includes a controller 50 to process the image data beforegenerating the control signals for the inkjet ejectors to ejectcolorants. Colorants can be ink or any suitable substance that includesone or more dyes or pigments and that is applied to the selected media.The colorant can be black, or any other desired color, and some printerconfigurations apply a plurality of distinct colorants to the media. Inthe configuration of FIG. 1, the printer 5 ejects cyan, magenta, yellow,and black (CMYK) inks onto the media web to form color ink images. Themedia includes any of a variety of substrates, including plain paper,coated paper, glossy paper, or transparencies, among others, and themedia can be available in sheets, rolls, or other physical formats.

The printer 5 is an example of a direct-to-sheet, continuous-media,phase-change inkjet printer that includes a media supply and handlingsystem configured to supply a long, substantially continuous, web ofmedia W of “substrate” (paper, plastic, or other printable material)from a media source, such as spool of media 10 mounted on a web roller8. For simplex printing, the printer 5 passes the media web W through amedia conditioner 16, print zone 20, printed web conditioner 80, andrewind unit 90 once. In the simplex operation, the media source 10 has awidth that substantially covers the width of the rollers over which themedia travels through the printer.

For duplex operations, the web inverter 84 turns the media web W over topresent a second side of the media to the printhead units 21A to 21Dforming print zone 20 and to the printed web conditioner 80, before themedia is taken up by the rewind unit 90. In a duplex operation, the webtravels over about one-half of the longitudinal length of each roller 26in the print zone 20 and printed web conditioner 80. The inverter 84flips and laterally displaces the media web W so the media web Wsubsequently travels over the other half of the longitudinal length ofeach roller 26 through the print zone 20 and printed web conditioner 80to print and condition the reverse side of the media web W. The rewindunit 90 is configured to wind the web onto a roller for removal from theprinter and subsequent processing.

In another duplex printing configuration, two printers with theconfiguration of the printer 5 are arranged serially with a web inverterinterposed between the two printers to perform duplex printingoperations. In the serial printing arrangement, the first printer formsand fixes an image on one side of a web, the inverter turns the webover, and the second printer forms and fixes an image on the second sideof the web. In the serial duplex printing configuration, the width ofthe media web W can substantially cover the longitudinal length of therollers in both printers over which the media travels during duplexprinting.

The media web W is unwound from the source 10 as needed and a variety ofmotors, not shown, rotate one or more rollers 12 and 26 to propel themedia web W. The media conditioner includes rollers 12 and a pre-heater18. The rollers 12 and 26 control the tension of the unwinding media asthe media moves along a path through the printer. In alternativeembodiments, the printer transports a cut sheet media through the printzone, in which case the media supply and handling system includes anysuitable device or structure to enable the transport of cut media sheetsalong a desired path through the printer. The pre-heater 18 brings theweb to an initial predetermined temperature that is selected for desiredimage characteristics corresponding to the type of media being printedas well as the type, colors, and number of inks being used. Thepre-heater 18 can use contact, radiant, conductive, or convective heatto bring the media to a target preheat temperature.

The media is transported through a print zone 20 that includes a seriesof color printhead modules or units 21A, 21B, 21C, and 21D, eachprinthead unit effectively extends across the width of the media and isable to eject ink directly onto the moving media. In printer 5, each ofthe printheads ejects a single color of ink, one for each of the colorstypically used in color printing, namely, cyan, magenta, yellow, andblack (CMYK) for printhead units 21A, 21B, 21C, and 21D, respectively.The controller 50 of the printer receives velocity data from encodersmounted proximately to rollers positioned on either side of the portionof the path opposite the four printheads to calculate the linearvelocity and position of the web as the web moves past the printheadunits. The controller 50 uses these data to generate firing signals foractuating the inkjet ejectors in the printhead arranged in the printheadunits to enable the printheads to eject four colors of ink withappropriate timing and accuracy for registration of the differentlycolored patterns to form color images on the media. The inkjet ejectorsactuated by the firing signals correspond to digital data processed bythe controller 50, which can be transmitted to the printer, generated bya scanner (not shown) that is a component of the printer, or otherwisegenerated and delivered to the printer. In various configurations, acolor module for each primary color includes one or more printheads,multiple printheads in a module are formed into a single row or multiplerow array, printheads of a multiple row array are staggered, a printheadprints more than one color, or the printheads or portions thereof aremounted movably in a direction transverse to the process direction P forprinting operations. While the printhead units in the printer 5 areconfigured to eject liquid drops of a phase change ink onto the mediaweb W, a similar configuration of inkjets that print solvent inks,aqueous inks, or any other liquid ink can be used to generate color inkimages as described herein.

A backing member 24A-24D, typically in the form of a bar or roll, isassociated with each color module and is arranged substantially oppositethe printhead units on the back side of the media. Each backing memberpositions the media at a predetermined distance from the printheads inthe printhead unit opposite the backing member. The backing members24A-24D are optionally configured to emit thermal energy to heat themedia to a predetermined temperature, and the various backer members canbe controlled individually or collectively. The pre-heater 18, theprintheads, backing members 24A-24D (if heated), as well as thesurrounding air combine to maintain the media along the portion of thepath opposite the print zone 20 in a predetermined temperature rangethat is suitable for the media to receive ejected ink from theprintheads.

As the partially-imaged media web W moves to receive inks of variouscolors from the printheads of the print zone 20, the printer 5 maintainsthe temperature of the media web within a predetermined range. Theprintheads in the color modules 21A-21D eject ink at a temperaturetypically significantly higher than the temperature of the media web W.Consequently, the ink heats the media, and the printer 5 includestemperature control devices to maintain the media web temperature withinthe predetermined range. For example, air blowers or fans can beutilized to facilitate control of the media temperature. Thus, theprinter 5 maintains the temperature of the media web W within anappropriate range for the jetting of all inks from the printheads of theprint zone 20. Temperature sensors (not shown) can be positioned alongthis portion of the media path to enable regulation of the mediatemperature.

Following the print zone 20 along the media path are one or more“mid-heaters” 30. A mid-heater 30 can use contact, radiant, conductive,and/or convective heat to control a temperature of the media. Themid-heater 30 brings the ink placed on the media to a temperaturesuitable for desired properties when the ink on the media is sentthrough the spreader 40. In one embodiment, a useful range for a targettemperature for the mid-heater is about 35° C. to about 80° C. Themid-heater 30 has the effect of equalizing the ink and substratetemperatures to within about 15° C. of each other. Lower ink temperatureresults in less line spread while higher ink temperature causes the inkimage to be visible from the non-printed side of the media. In oneembodiment, the mid-heater 30 adjusts substrate and ink temperatures to0° C. to 20° C. above the temperature of the spreader.

Following the mid-heaters 30, a fixing assembly 40 applies heat and/orpressure to the media to fix the images to the media. The fixingassembly includes any suitable device or apparatus for fixing images tothe media including heated or unheated pressure rollers, radiantheaters, heat lamps, and the like. In the embodiment of the FIG. 7, thefixing assembly 40 includes a spreader roller 42 and a pressure roller100, which apply a predetermined pressure, and in some implementations,heat, to the media. The function of the fixing assembly 40 is to flattenthe individual ink droplets, strings of ink droplets, or lines of ink onweb W with pressure and, in some systems, heat. The fixing assembly 40flattens the ink drops to fill spaces between adjacent drops and improvethe uniformity of the images on the media web W. In addition tospreading the ink, the fixing assembly 40 improves fixation of the inkimage to the media web W by increasing ink layer cohesion and/orincreasing the ink-web adhesion. The spreader roller 42 can include heatelements, such as heating elements 46, to bring the web W to atemperature in a range from about 35° C. to about 80° C.

In one practical embodiment, the spreader roller 42 in fixing assembly40 is maintained at an optimum temperature that depends on theproperties of the ink, for example, 55° C. Generally, a lower rollertemperature gives less line spread while a higher temperature canproduce imperfections in the gloss of the ink image. Roller temperaturesthat are too high may cause ink to offset to the roller. In onepractical embodiment, the pressure roller 100 is pressed into thespreader roller 42 with a force of approximately 3000 pounds at each endof the pressure roller 100. As described in detail below, the pressureroller 100 of the fixing assembly 40 is partially filled with a fluid180 to increase the temperature uniformity of the pressure roller 100.

The fixing assembly 40 can include a cleaning/oiling station 48associated with the spreader roller 42. The station 48 cleans and/orapplies a layer of some release agent or other material to the surfaceof the spreader roller 42 to disable the ink from adhering to thesurface of the spreader roller 42.

Following passage through the spreader 40 the printed media can bedirected to the web inverter 84 for inversion of the print medium anddisplacement to another section of the rollers for a second pass by theprintheads, mid-heaters, spreader, and coating station. Alternatively,the media web W can be wound onto a roller for removal from the systemafter a simplex printing operation or after printing the second side ofa duplex operation. One configuration of the printer 5 winds the simplexor duplex printed media onto a roller for removal from the system byrewind unit 90. Alternatively, the media can be directed to otherprocessing stations that perform tasks such as cutting, binding,collating, and/or stapling the media or the like.

While the embodiment of FIG. 1 illustrates a direct-to-media continuousfeed printer, the reader should appreciate that the pressure rollercontaining fluid can be used in other types of printers as well. Forexample, the fluid-containing pressure roller can be used in an indirectprinter or in a cut-sheet imaging device. Furthermore, thefluid-containing pressure roller described herein can be used in othermedia processing devices that transport heated media through a nip, forexample, a high pressure laminating device.

FIG. 2 depicts a cross-sectional view of the pressure roller 100 of theprinter 5. The pressure roller 100 includes a hollow cylindrical member120, an elastomeric layer 160, a first endbell 172, and a second endbell176. A chamber 140 is defined within the hollow cylindrical member 120between the first 172 and second 176 endbells. The chamber 140 isconfigured to store a predetermined quantity of fluid 180, which absorbsheat from the hollow cylindrical member 120.

The hollow cylindrical member 120 defines an inner wall 124, an outerwall 128, a first end 132, and a second end 136. The first 132 andsecond 136 ends of the hollow cylindrical member 120 are configured toaccommodate the first endbell 172 and second endbell 176, respectively,which can be welded or otherwise sealingly connected to the inner wall124 of the hollow cylindrical member 120. In one embodiment, the hollowcylindrical member 120 and endbells 172 and 176 substantially comprisestainless steel, for example, type 304 stainless steel, though othersuitable materials can be used in different embodiments.

The inner wall 124 of the hollow cylindrical member 120 and the endbells172 and 176 define the chamber 140. In the embodiment of FIG. 2, thechamber 140 is cylindrical, extending from a portion of the inner wall124 to a diametrically opposed portion of the inner wall 124 around theentire circumference of the inner wall 124. In other words, the chamber140 is cylindrical and includes no elements positioned within thechamber 140.

The chamber 140 is configured to be partially filled with a fluid 180,which can be water, antifreeze, or another suitable liquid. One or bothof the endbells 172 and 176 can include a plug (not shown) to enablefilling and emptying of the fluid 180 in the chamber 140. In oneembodiment, the chamber 140 is configured to be filled withapproximately one and a half gallons (5.7 liters) of fluid 180, thoughthe amount of fluid in the chamber can vary depending on the size andthe desired thermal characteristics of the pressure roller.

The elastomeric layer 160 coats the outer wall 128 of the hollowcylindrical member 120. The elastomeric layer 160 includes an outersurface 164 that is configured to contact a spreader roller, such asspreader roller 42 of FIG. 1, to form a pressure nip through which themedia web is transported to spread and fix ink to the media web. Theelastomeric layer 160 has a first thickness at the first 132 and second136 ends of the hollow cylindrical member 120, and a second thickness atthe center of the hollow cylindrical member 120. The thickness at thecenter of the hollow cylindrical member 120 is typically greater thanthe thickness at the ends 132 and 136 to enable the outer surface 164 ofthe elastomeric layer 160 to have a crowned profile. In one embodiment,the elastomeric layer 160 substantially comprises polyurethane with athickness of 2.5 millimeters in the center and 2.475 millimeters at theends 132 and 136 of the roller. In other embodiments, the elastomericlayer can comprise other suitable materials, such as nitrile butadienerubber (“NBR”), and can be formed with a different thickness.

In operation, the pressure roller 100 is mounted in a printer, such asprinter 5, and configured to form a nip with a spreader roller, such asspreader roller 42. A media web, on which an ink image has been formed,is fed through the nip formed between the spreader roller and thepressure roller 100. The media web is heated and the ink image on themedia web includes a plurality of heated ink drops, both of which resultin heat transferring to the pressure roller 100. The heat from the inkand media web is absorbed by the elastomeric layer 160 and the hollowcylindrical member 120.

In a pressure roller that does not contain fluid, the absorbed heat cancause the temperature of the pressure roller to increase, particularlynear the center of the roller. As the temperature of the rollerincreases, the roller develops thermal gradients, resulting in portionsof the pressure roller expanding and changing the shape of the roller.The change in the roller shape alters the ability of the nip formedbetween the pressure roller and the spreader roller to pass mediawithout wrinkling. In particular, the center of the roller tends toexpand, causing the pressure roller to develop a barrel shape. Axialvelocity differentials in the nip form as a result of creep energycaused by the non-uniform thermal expansion of the pressure roller,which can produce wrinkling of the media as it passes through the nip.The media wrinkle problems are exacerbated in the context of solid inkprinting, as the solid ink can adhere to the pressure roller, reducingthe coefficient of friction between the media and the pressure roller.The reduced friction between the pressure roller and media incombination with the velocity differentials in the nip wrinkles themedia in the nip.

Furthermore, increased temperature in the pressure roller can reduce themodulus of the elastomeric layer. In response to the reduced modulus,less pressure is generated in the nip between the pressure roller andthe spreader roller, further reducing the force that holds the mediaagainst the pressure roller as it moves through the nip. The reducedpressure at the nip enables the creep forces generated by velocitydifferentials to have a greater effect on the media, compounding mediawrinkle problems.

As pressure roller 100 contacts heated media moving through the nip,heat is transferred from the media to the elastomeric layer 160 and thehollow cylindrical member 120. The fluid 180 in pressure roller 100 isconfigured to absorb the heat from the hollow cylindrical member 120 andelastomeric layer 160. The volumetric heat capacity of the fluid 180 issignificantly greater than that of the hollow cylindrical member 120,resulting in an increased overall heat capacity of the pressure roller100. The pressure roller 100 is therefore able to resist increases intemperature of the pressure roller 100 during printing processes, whichminimizes the thermal effects on the modulus of the elastomeric layer160 and reduces thermal expansion of the hollow cylindrical member 120.

Furthermore, as the media is fed through the nip between the pressureroller 100 and the spreader roller, the pressure roller 100 rotatesabout a center axis, which agitates the fluid 180 inside the chamber140. As the fluid 180 moves within the chamber 140, the heated portionsof the fluid 180 are mixed along the axis of the hollow cylindricalmember 120 with cooler portions of the fluid 180. Thus, the fluid 180remains at a relatively uniform temperature along the axis of the hollowcylindrical member 120. Because the heat capacity of the fluid 180 isgreater than the heat capacity of the hollow cylindrical member 120, thetemperature of the hollow cylindrical member 120 remains near thetemperature of the fluid 180 along the entire axial length of the hollowcylindrical member 120, enhancing the temperature uniformity of thehollow cylindrical member 120. Thermal expansion of the hollowcylindrical member 120 is therefore uniform along the axial length ofthe hollow cylindrical member 120, which enables the nip profile to beunaffected by temperature increases of the hollow cylindrical member120. This uniform thermal expansion enables the nip to retain a profilethat reduces media wrinkle, for example, a “zero-crown” profile, whichpulls the media web toward the ends 132 and 136 of the pressure roller100 to prevent the media from wrinkling in the nip.

FIG. 3 depicts a cross-sectional view of another embodiment of apressure roller 200. The pressure roller 200 includes a hollowcylindrical member 220, an elastomeric layer 260, a first endbell 272,and a second endbell 276. A chamber 240 is defined within the hollowcylindrical member 240 between the first 272 and second 276 endbells.The chamber 240 is configured to store a predetermined quantity of fluid280, which absorbs heat from the hollow cylindrical member 220.

The hollow cylindrical member 220 defines an inner wall 224, an outerwall 228, a first end 232, and a second end 236. The first 232 andsecond 236 ends of the hollow cylindrical member 220 are configured suchthat the first endbell 272 and second endbell 276 are sealinglyconnected to the inner wall 224 of the hollow cylindrical member 220 atthe ends 232 and 236, respectively. The inner wall 224 includes aplurality of fins 284 that project from the inner wall 224 and arespaced within the chamber 240 circumferentially and axially. The fins284 are configured to increase the mixing of the fluid 280 in thechamber 240 as the pressure roller 200 rotates.

The inner wall 224 of the hollow cylindrical member 220 and the endbells272 and 276 define the chamber 240. The chamber 240 is cylindrical, withthe exception of the fins 284 projecting from the inner wall 224. Thechamber 240 is configured to be partially filled with a fluid 280 toabsorb and spread heat from the hollow cylindrical member 220.

The elastomeric layer 260 coats the outer wall 228 of the hollowcylindrical member 220. The elastomeric layer 260 includes an outersurface 264 that is configured to contact a spreader roller to form apressure nip through which the media web is transported to spread andfix ink to the media web. The elastomeric layer 260 has a firstthickness at the first 232 and second 236 ends of the hollow cylindricalmember 220, and a second thickness in the center of the hollowcylindrical member 220. The elastomeric layer 260 has a crowned profile,meaning that the elastomeric layer 260 is thicker at the center of theroller 200 than at the ends 232 and 236 of the roller 200.

The pressure roller 200 operates in substantially the same manner as thepressure roller 100 described above with reference to FIG. 1 and FIG. 2.However, as the pressure roller 200 rotates about the center axis, thefins 284 supplement the agitation of the fluid 280 inside the chamber240. Agitating the fluid 280 with fins 284 further mixes the fluid 280and spreads the heat absorbed throughout the volume of fluid 280,enabling enhanced temperature uniformity throughout the hollowcylindrical member 220 and elastomeric layer 260.

FIG. 4 depicts a cross-sectional view of another embodiment of apressure roller 300. The pressure roller 300 includes a hollowcylindrical member 320, an elastomeric layer 360, a first endbell 372,and a second endbell 376. A chamber 340 is defined within the hollowcylindrical member 340 between the first 372 and second 376 endbells.The chamber 340 is configured to store a predetermined quantity of fluid380, which absorbs heat from the hollow cylindrical member 320.

The hollow cylindrical member 320 defines an inner wall 324, an outerwall 328, a first end 332, and a second end 336. The first 332 andsecond 336 ends of the hollow cylindrical member 320 are configured suchthat the first endbell 372 and second endbell 376 are sealinglyconnected to the inner wall 324 of the hollow cylindrical member 320 atthe ends 332 and 336, respectively. The inner wall 324 includes aplurality of paddles 388 projecting from the inner wall 324, which arespaced at different positions along the circumference of the inner wallof the chamber and extend axially along the inner wall of the chamber340. The paddles could also be spaced at different positions along theaxial length of the inner wall of the chamber and extendcircumferentially along a portion of the inner wall of the chamber 340.The paddles 388 are configured to increase the mixing of the fluid 380in the chamber 340 as the pressure roller 300 rotates.

The inner wall 324 of the hollow cylindrical member 320 and the endbells372 and 376 define the chamber 340. The chamber 340 is cylindrical, withthe exception of the paddles 388 projecting from the inner wall 324. Thechamber 340 is configured to be partially filled with a fluid 380 thatabsorbs heat from the hollow cylindrical member 320.

The elastomeric layer 360 coats the outer wall 328 of the hollowcylindrical member 320. The elastomeric layer 360 includes an outersurface 364 that is configured to contact a spreader roller to form apressure nip through which the media web is transported to spread andfix ink to the media web. The elastomeric layer 360 has a crownedprofile, meaning that the elastomeric layer 360 is thicker at the centerof the roller 300 than at the ends 332 and 336 of the roller 300.

The pressure roller 300 operates in substantially the same manner as thepressure roller 100 described above with reference to FIG. 1 and FIG. 2.However, as the pressure roller 300 rotates about the center axis, thepaddles 388 supplement the agitation of the fluid 380 inside the chamber340. Agitating the fluid 380 with paddles 388 further mixes the fluid380 and distributes the heat absorbed throughout the volume of fluid380, enabling enhanced temperature uniformity throughout the hollowcylindrical member 320 and elastomeric layer 360.

FIG. 5 depicts a cross-sectional view of another pressure roller 400.The pressure roller 400 includes a hollow cylindrical member 420, anelastomeric layer 460, a first endbell 472, a second endbell 476, and asolid rod 492. A chamber 440 is defined within the hollow cylindricalmember 440 between the first 472 and second 476 endbells. The chamber440 is configured to store a predetermined quantity of fluid 480, whichabsorbs heat from the hollow cylindrical member 420. The solid rod 492extends axially through the center of the hollow cylindrical member 420from the first endbell 472 to the second endbell 476 and includes aplurality of fins 484 projecting outwardly from the solid rod 492. Thefins 484 are configured to increase the mixing of the fluid 480 in thechamber 440 as the pressure roller 400, including the solid rod 492,rotates.

The hollow cylindrical member 420 defines an inner wall 424, an outerwall 428, a first end 432, and a second end 436. The first 432 andsecond 436 ends of the hollow cylindrical member 420 are configured suchthat the first endbell 472 and second endbell 476 are sealinglyconnected to the inner wall 424 of the hollow cylindrical member 420 atthe ends 432 and 436, respectively.

The inner wall 424 of the hollow cylindrical member 420, the endbells472 and 476, and the outer surface of the solid rod 492 define thechamber 440. The chamber 440 is in the shape of an annular cylinder,with the exception of the fins 484 projecting from the solid rod 492into the chamber 440. The chamber 440 is configured to be partiallyfilled with a fluid 480 that absorbs heat from the hollow cylindricalmember 420.

The elastomeric layer 460 coats the outer wall 428 of the hollowcylindrical member 420. The elastomeric layer 460 includes an outersurface 464 that is configured to contact a spreader roller to form apressure nip through which the media web is transported to spread andfix ink to the media web. The elastomeric layer 460 has a crownedprofile, meaning that the elastomeric layer 460 is thicker at the centerof the roller 400 than at the ends 432 and 436 of the roller 400.

The pressure roller 400 operates in substantially the same manner as thepressure roller 100 described above with reference to FIG. 1 and FIG. 2.However, as the pressure roller 400 and solid rod 492 rotate about thecenter axis, the fins 484 supplement the agitation of the fluid 480inside the chamber 440. Agitating the fluid 480 with fins 484 furthermixes the fluid 480 and spreads the heat absorbed throughout the volumeof fluid 480, enabling enhanced temperature uniformity throughout thehollow cylindrical member 420.

FIG. 6 depicts a cross-sectional view of another embodiment of apressure roller 500. The pressure roller 500 includes a hollowcylindrical member 520, an elastomeric layer 560, a first endbell 572, asecond endbell 576, and a solid rod 592. A chamber 540 is defined withinthe hollow cylindrical member 540 between the first 572 and second 576endbells. The chamber 540 is configured to store a predeterminedquantity of fluid 580, which absorbs heat from the hollow cylindricalmember 520. The solid rod 592 extends axially through the center of thehollow cylindrical member 520 from the first endbell 572 to the secondendbell 576 and includes a plurality of paddles 588 projecting outwardlyfrom the solid rod 592. The paddles 588 are configured to increase themixing of the fluid 580 in the chamber 540 as the pressure roller 500,including the solid rod 592, rotates.

The hollow cylindrical member 520 defines an inner wall 524, an outerwall 528, a first end 532, and a second end 536. The first 532 andsecond 536 ends of the hollow cylindrical member 520 are configured suchthat the first endbell 572 and second endbell 576 are sealinglyconnected to the inner wall 524 of the hollow cylindrical member 520 atthe ends 532 and 536, respectively.

The inner wall 524 of the hollow cylindrical member 520, the endbells572 and 576, and the outer surface of the solid rod 592 define thechamber 540. The chamber 540 is in the shape of an annular cylinder,with the exception of the paddles 588 projecting from the solid rod 592into the chamber 540. The paddles 588 can extend in a relativelystraight line along a portion of the axial length of the solid rod 592and extend into the chamber 540 an appropriate distance without touchingthe inner wall of the chamber 540. Alternatively, the paddles can followall or a portion of the circumference of the solid rod 592 either in acircular or helical pattern. The chamber 540 is configured to bepartially filled with a fluid 580 that absorbs heat from the hollowcylindrical member 520.

The elastomeric layer 560 coats the outer wall 528 of the hollowcylindrical member 520. The elastomeric layer 560 includes an outersurface 564 that is configured to contact a spreader roller to form apressure nip through which the media web is transported to spread andfix ink on the media web. The elastomeric layer 560 has a crownedprofile, meaning that the elastomeric layer 560 is thicker at the centerof the roller 500 than at the ends 532 and 536 of the roller 500.

The pressure roller 500 operates in substantially the same manner as thepressure roller 100 described above with reference to FIG. 1 and FIG. 2.However, as the pressure roller 500 and solid rod 592 rotate about thecenter axis, the paddles 588 supplement the agitation of the fluid 580inside the chamber 540. Agitating the fluid 580 with paddles 588 furthermixes the fluid 580 and spreads the heat absorbed throughout the volumeof fluid 580, enabling enhanced temperature uniformity along the axiallength of the hollow cylindrical member 520.

It will be appreciated that variations of the above-disclosed apparatusand other features, and functions, or alternatives thereof, may bedesirably combined into many other different systems or applications.Various presently unforeseen or unanticipated alternatives,modifications, variations, or improvements therein may be subsequentlymade by those skilled in the art, which are also intended to beencompassed by the following claims.

What is claimed is:
 1. A pressure roller for a media processing devicecomprising: a hollow cylindrical member having a first end, a secondend, an inner cylindrical wall, and an outer cylindrical wall, the innercylindrical wall forming a chamber that extends between diametricallyopposed portions of the inner cylindrical wall around an entirecircumference of the inner cylindrical wall and that extends from thefirst end to the second end of the hollow cylindrical member, the innercylindrical wall having at least one paddle extending from the innercylindrical wall; an elastomeric layer positioned immediately adjacentto the outer cylindrical wall and surrounding the outer cylindrical wallfrom the first end to the second end of the hollow cylindrical member,the elastomeric layer defining an outer surface of the pressure roller;a first endbell sealingly connected to the first end of the hollowcylindrical member; a second endbell sealingly connected to the secondend of the hollow cylindrical member, the first endbell and the secondendbell preventing ingress and egress of fluid from the chamber withinthe hollow cylindrical member; and a volume of a fluid within thechamber that fills no more than ninety-five percent of the chamber toabsorb heat transferred to the hollow cylindrical member by anotherroller forming a nip with the hollow cylindrical member, the at leastone paddle extending from the inner cylindrical wall being configured tomix the fluid within the chamber to distribute the heat absorbed by thehollow cylindrical member throughout the fluid as the hollow cylindricalmember rotates to enable uniform thermal expansion of the hollowcylindrical member in the nip.
 2. The pressure roller of claim 1, theinner cylindrical wall of the hollow cylindrical member furthercomprising: at least one fin extending from the inner cylindrical wall,the at least one fin being configured to mix the fluid and distributethe heat absorbed by the hollow cylindrical member within the chamber toenable uniform thermal expansion of the hollow cylindrical member in thenip.
 3. The pressure roller of claim 1 wherein the hollow cylindricalmember is substantially comprised of stainless steel.
 4. The pressureroller of claim 1 wherein the elastomeric layer is substantiallycomprised of polyurethane.
 5. The pressure roller of claim 1 wherein anouter diameter of the elastomeric layer at the first and second ends ofthe hollow cylindrical member is less than an outer diameter of theelastomeric layer at a center portion of the hollow cylindrical member.6. The pressure roller of claim 1, the outer surface of the elastomericlayer being configured to contact the other roller under pressure toform the nip.
 7. A pressure roller for a media processing devicecomprising: a hollow cylindrical member having a first end, a secondend, an inner cylindrical wall, and an outer cylindrical wall, the innercylindrical wall forming a chamber that extends between diametricallyopposed portions of the inner cylindrical wall around an entirecircumference of the inner cylindrical wall and that extends from thefirst end to the second end of the hollow cylindrical member; anelastomeric layer positioned immediately adjacent the outer cylindricalwall and surrounding the outer cylindrical wall from the first end tothe second end of the hollow cylindrical member, the elastomeric layerdefining an outer surface of the pressure roller; a first endbellsealingly connected to the first end of the hollow cylindrical member; asecond endbell sealingly connected to the second end of the hollowcylindrical member, the first endbell and the second endbell preventingingress and egress of fluid from the chamber within the hollowcylindrical member; a solid rod extending axially through the center ofthe hollow cylindrical member from the first endbell to the secondendbell, the solid rod having at least one paddle extending from theouter surface of the solid rod; and a volume of a fluid within thechamber that fills no more than ninety-five percent of the chamber toabsorb heat transferred to the hollow cylindrical member by anotherroller forming a nip with the hollow cylindrical member, the at leastone paddle extending from the solid rod being configured to mix thefluid and distribute the heat absorbed by the hollow cylindrical memberthroughout the fluid as the hollow cylindrical member rotates to enableuniform thermal expansion of the hollow cylindrical member in the nip.8. The pressure roller of claim 7, the exterior surface of the solid rodfurther comprising: at least one fin extending from the outer surface ofthe solid rod, the at least one fin being configured to mix the fluidand distribute the heat absorbed by the hollow cylindrical member withinthe chamber to enable uniform thermal expansion of the hollowcylindrical member in the nip.
 9. The pressure roller of claim 7 whereinthe hollow cylindrical member is substantially comprised of stainlesssteel.
 10. The pressure roller of claim 7 wherein the elastomeric layeris substantially comprised of polyurethane.
 11. The pressure roller ofclaim 7 wherein an outer diameter of the elastomeric layer at the firstand second ends of the hollow cylindrical member is less than an outerdiameter of the elastomeric layer at a center portion of the hollowcylindrical member.
 12. The pressure roller of claim 7, the outersurface of the elastomeric layer being configured to contact the otherroller under pressure to form the nip.
 13. A printing machinecomprising: a first roller; a second roller including: a hollowcylindrical member having a first end, a second end, an innercylindrical wall, and an outer cylindrical wall, the inner cylindricalwall forming a chamber that extends between diametrically opposedportions of the inner cylindrical wall around an entire circumference ofthe inner cylindrical wall and that extends from the first end to thesecond end of the hollow cylindrical member; an elastomeric layerconnected immediately adjacent to the outer cylindrical wall,surrounding the outer cylindrical wall from the first end to the secondend of the hollow cylindrical member; a first endbell sealinglyconnected to the first end of the hollow cylindrical member; a secondendbell sealingly connected to the second end of the hollow cylindricalmember, the first endbell and the second endbell preventing ingress andegress of fluid from the chamber within the hollow cylindrical member ofthe second roller; a volume of a fluid within the chamber that fills nomore than ninety-five percent of the chamber to absorb heat transferredto the hollow cylindrical member by the first roller that forms a nipwith the elastomeric layer of the second roller and to distribute theheat absorbed from the first roller throughout the fluid as the hollowcylindrical member rotates to enable uniform thermal expansion of thehollow cylindrical member in the nip; and at least one paddle extendingfrom the inner cylindrical wall of the hollow cylindrical member, the atleast one paddle being configured to mix fluid and distribute heatabsorbed by the hollow cylindrical member within the chamber to enableuniform thermal expansion of the hollow cylindrical member in the nip; aplurality of printheads configured to eject ink drops onto a media web;and a media transport configured to move the media web through the nipafter the ink drops have been ejected onto the media web to spread theink drops and form an ink image on the media web.
 14. The printingmachine of claim 13, the second roller further comprising: at least onefin extending from the inner cylindrical wall, the at least one finebeing configured to mix the fluid and distribute the heat absorbed bythe hollow cylindrical member within the chamber to enable uniformthermal expansion of the hollow cylindrical member in the nip.
 15. Theprinting machine of claim 13 wherein the hollow cylindrical member issubstantially comprised of stainless steel.
 16. The printing machine ofclaim 13 wherein the elastomeric layer is substantially comprised ofpolyurethane.
 17. The printing machine of claim 13 wherein an outerdiameter of the elastomeric layer at the first and second ends of thehollow cylindrical member is less than an outer diameter of theelastomeric layer at a center portion of the hollow cylindrical member.